In the Southern Ocean, the Lysianassoidea is one of the most important amphipod groups, both in terms of species number and abundance. DNA taxonomy and phylogeographic studies were conducted to detect cryptic diversity and to test the circumpolarity and eurybathy of some taxa. These studies demonstrated that several morphospecies are species complexes with allo- and sympatric distributions and revealed a number of undescribed species. Molecular phylogenies were constructed, using mitochondrial and nuclear genes, providing a framework for a systematic revision of the taxa and testing the hypotheses concerning the colonization of the abyssal basins from the shelf and vice versa.